Catapults
Historical Overview - This device is used in ancient times by greeks and chinese around 9th century as a
military weapon and this device is being evolved over the centuries as an crucial army weapon. While
nowadays catapults are mostly no longer used in military conflicts, they remain an essential part of history,
showcasing the continuous improvement of ancient engineers and their contribution to the evolution of
military technology.
Prerequisites and Learning Objectives
Prerequisites Learning Objectives
Science 1. Students will able to explain how a
catapult works, including the principles
1. Basic understanding of Simple Machine.
of potential and kinetic energy.
2. Basic knowledge of forms of Energy
(kinetic & Potential).
2. Students will be able to apply
mathematical concepts to calculate
3. Force & Motion. variables like launch angle, distance, and
velocity.
Mathematics 3. To design and build a functional catapult,
1. Graphical solutions of equations. considering factors like materials,
2. Applications of Trigonometry. dimensions, and mechanical advantage.
3. Coordinate Geometry
1. During ancient times, how were heavy stones or objects lifted during construction, and what sorts
of mechanical tools were employed for this purpose?
2. When we shoot bullets from a gun, we experience a backward recoil. What causes this backward
recoil sensation?
3. What's the reason for pulling the arrow backward when using a bow in archery?
4. What is one of the key factors in cricket to achieve the highest bowling speed?
5. When Rubber band is stretched why it tries harder to regain its original shape and size?
Scientific Principle
To understand the scientific Principle of catapults let’s first begin by conducting a hands-on activity
using a rubber band.
In this activity you will observe that rubber is an
example of elastic material, so once you stretch your
rubber it deforms its shape and you will feel that it
tries very hard to get back in its original shape.
While performing the activity don’t you find it is
harder to stretch rubber band beyond a certain point?
The phenomenon behind this activity is its Elasticity.
Elasticity
In that activity we observed that the Rubber band is pulled back and trying its best to get back into its
initial position and that is because of the property of material which is Elasticity.
What is Elasticity?
Elasticity is a ability of a body to resist and to return into its original size and shape after the applied
force is removed. In this process the material conserves its energy to shoot back itself from the
Potential energy to Kinetic energy.
Making of Catapult.
Before understanding the principle of Catapult it's very necessary to understand the making of
Catapult.
Base - To make any device or object you need a perfect solid base for the
balancing and load bearing of whole catapult.
Throwing Arm - By applying the understanding of previous lecture
Law of Lever we will construct a throwing arm in which it will be joined
by the fulcrum from the base and support bars with the ratio of 1:4.
Counterweight - A counterweight will be used as an applied force for the
catapult which will work against the gravity.
Sling - A place where you can keep your throwing object and sling is a
flexible arm which allows catapult to throw it farther.
Trigger - When the pin is removed, the counterweight falls due to
gravity, creating a powerful force that propels the throwing arm upward,
launching the object. This is a key feature of how trebuchets operate..
Now, how does a principle of Elasticity relates to Catapult?
In a rubber band activity we have seen that when a force is applied over the rubber band to stretch it
and it attains a high level of energy and when at the point where applied force is removed it instantly
shoots the paper with tremendous force by converting potential energy into kinetic energy.
This principal is exactly applied on the catapult
1. Instead of a Rubber band, we employ a Throwing Arm that reflects the behavior of a rubber band
when an external force is applied. By utilizing the principles of leverage (law of lever), and this
Throwing Arm produces four times the force applied by the counterweight because it is fixed by the
fulcrum in a 1:4 ratio.
2. Where at the place of Applied Force we use Counterweight in which it is tied with the rope against
the gravity which ensures that the throwing arm remains at the static downwards position to obtain and
conserve the Potential Energy.
Final Outcome
In the initial frame, you'll observe that when
the counterweight is connected, it exerts a
downward force on the throwing arm. The
throwing arm is securely positioned at an
elevated point, countering the force of
gravity, due to the presence of a rope.
In the second frame, we notice the removal
of a trigger, causing the counterweight to
fall down under the force of gravity.
Simultaneously, the throwing arm instantly
converts its potential energy into kinetic
energy, while the sling propels the object to
a considerable distance.
Mathematical Applications of Catapult
When we talk about catapult as a war weapon so it’s very important to calculate the distance which
will be covered by
